In a UMTS (Universal Mobile Telecommunications System) network, long-term evolution (LTE) is under study for the purposes of further increasing high-speed data rates, providing low delay, and so on (non-patent literature 1). In LTE, as multiple access schemes, a scheme that is based on OFDMA (Orthogonal Frequency Division Multiple Access) is used in downlink channels (the downlink), and a scheme that is based on SC-FDMA (Single Carrier Frequency Division Multiple Access) is used in uplink channels (the uplink).
In LTE, MIMO (Multi Input Multi Output) is defined to improve the data rates (spectral efficiency) by transmitting/receiving data using a plurality of antennas. In MIMO, a plurality of transmitting/receiving antennas are provided in a transmitter/receiver, and different transmitting antennas of the transmitting side transmit different transmission information sequences simultaneously. On the receiving side, information sequences that are transmitted simultaneously are separated and detected by utilizing the fact that different fading variation is produced between transmitting/receiving antennas.
As MIMO transmission schemes, single-user MIMO (SU-MIMO (Single User MIMO)), which transmits transmission information sequences for the same user from different transmitting antennas at the same time, and multi-user MIMO (MU-MIMO (Multiple User MIMO)), which transmits transmission information sequences for different users from different transmitting antennas at the same time, are proposed. In SU-MIMO and MU-MIMO, optimal PMIs (Precoding Matrix Indicators) corresponding to the amount of phase/amplitude control (precoding weights) to be set in antennas are selected from a codebook, and are fed back to a transmitter as channel information (CSI: Channel State Information). On the transmitter side, each transmitting antenna is controlled based on the PMIs fed back from the receiver, and transmission information sequences are transmitted.